Cameras and other image recording devices often use one or more image sensors, such as a charged-coupled device (CCD) sensor or a complementary metal-oxide-semiconductor (CMOS) image sensor. A typical CMOS image sensor may include a two-dimensional array of pixels, where each pixel may include a photo detector, such as a photodiode, and one or more transistors to activate each pixel. An image sensor may be implemented in a rolling shutter configuration or a global shutter configuration.
In a rolling shutter, each of the pixels within the image sensor capture light row by row, and the captured light is then read out to a processor row by row. In this configuration, there may be a time delay between when the first pixel row captures light from the scene and when the last pixel row captures light from the scene. Accordingly, if there is movement in the scene between the first and last pixel rows, the movement may be captured as blurred lines or other motion artifacts. In a global shutter, each of the pixels capture light at the same time (i.e., have the same integration period) and then the pixels transfer the light to a storage component until the pixels can be read out by a processor. In a global shutter configuration, motion is captured and reproduced in an image that has less blurring than a rolling shutter, as each of the pixels capture light at the exact same time. However, in this configuration, the image sensor generally must include storage space for each pixel, which may require a reduction in resolution or an increase in size for the image sensor.
In some instances, the light signals corresponding to the images may include noise (e.g., due to residual charge left in the photodiode or photogate). To reduce noise, correlated double sampling may be used that resets a floating diffusion (or other storage node) after an initial read out and then reads the node a second time. However, for multiple images (such as a video or long exposure time), the photodiode or photogate may be reset multiple times during the length of exposure. In these instances, the captured signals readout between resets may be averaged together digitally, but this may introduce additional noise into the system.